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Lecture_11-1 - Circadian Rhythms Require Both Innate...

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Lecture 11 Notes Control of Daily and Seasonal Rhythms HOW does a bird time its daily and seasonal activities? What changes over the course of 24h? What changes seasonally? Circadian Rhythm – daily, rhythmic cycle lasting 24h Circannual Rhythm – rhythmic cycles lasting 12 months CIRDADIAN RHYTHMS Entrainment – synchronization of organisms to an external rhythm Ex. When on a standard light cycle, activity levels are the same every day. When there is no light cycle (Constant light or dark), activity rhythms free run. Free-Running Rhythms – rhythms that drift from normal cycles Innate internal rhythm – mechanism for keeping approximately 24h cycles without external cues Zeitgeber – literally “time giver”, cue used by animals to set circadian rhythms
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Unformatted text preview: Circadian Rhythms Require Both: Innate internal clock (clock genes!) Zeitgeber The major zeitgeber driving circadian processes is light. Pineal gland – triangular gland located in the top of the avian brain, detects light and produces the hormone melatonin. Superchiasmatic Nucleus (SCN) – pacemaker in the hypothalamus that controls the patterns of daily activities. Every cell in the body has an intrinsic rhythm. This is particularly important in the pineal gland, the eye, and the hypothalamus as they control much of the body’s activities both intrinsically and in response to darkness. Light can act in three places – the eye, the pineal, and an extraretinal/extrapineal receptor....
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Lecture_11-1 - Circadian Rhythms Require Both Innate...

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